The present invention relates to a hot plate unit having a casing and a heater.
In a semiconductor production process, there is performed a step in which a photosensitive resin is formed as an etching resist on a silicon wafer, and this silicon wafer is then etched by using an etchant. The application of the photosensitive resin onto the silicon wafer is carried out by using a coating apparatus such as a spin coater. In this case, since the applied photosensitive resin is in a liquid and unhardened state, a drying step is first performed to lower the fluidity of the resin to some extent, and the resin is then subjected to an exposure/development step.
As an apparatus for drying the silicon wafer, which has undergone the coating step, a hot plate unit, which employs a metal heater comprising an aluminum plate having the back surface on which a heating element is arranged, has been used. However, in the prior art hot plate unit, the metal heater must inevitably be thicken to prevent the generation of distortion due to thermal expansion, and hence, it is poor in point of temperature control.
Moreover, when the heater is heated, the casing is heated owing to radiant heat generated from the back surface of the heater, resulting in the rise of the temperature of the casing. That is, thermal energy which should inherently be used for heating the heater is partially used to heat the casing, resulting in the loss of the thermal energy. This increases a time required for increasing the heater temperature up to a predetermined temperature, which prolongs a time for the entire drying step, whereby the improvement of productivity tends to be disturbed. In addition, the casing is heated up to a temperature exceeding a heat resistance level of a metal material for the casing, which is not preferable.
To solve the aforementioned problem, there can be considered a method for filling a heat insulating material such as a glass fiber between the heater and the casing so as to shut out the radiant heat. This may prevent the excessive temperature rise of the casing, but the heat insulating material generates dusts, deteriorating an ambient environment. Therefore, such an apparatus is not appropriate for a semiconductor production field which requires a highly clean environment.
It is therefore an object of the invention to provide a hot plate unit having a reduced heater temperature rise time and not generating dusts.
To solve the aforementioned problems, a first aspect of the present invention provides a hot plate unit comprising a casing having an opening portion; a heater arranged on the opening portion and including a plate-shaped member made from ceramics and a heat generating element arranged on the plate-shaped member; and a plate-shaped reflection member interposed between the casing and the heater.
The plate-shaped reflection member is preferably at least one selected from a group consisting of a metal plate, a ceramic plate and a resin plate.
The ceramics are preferably nitride ceramics or carbide ceramics.
The plate-shaped reflection member is preferably arranged via a predetermined distance from the back surface of the heater and in parallel to the back surface.
The plate-shaped reflection member preferably comprises a plurality of plate-shaped members.
The plate-shaped reflection member preferably has reflection planes on both the sides thereof, respectively.
The plate-shaped reflection member preferably comprises a layer reflection member formed on an inner wall of the casing.
The plate-shaped reflection member preferably comprises a foil reflection member.
The casing and the heater are preferably arranged via a predetermined distance from each other.
The heater preferably has a plurality of terminal pins electrically connected to the heat generating element, and a plurality of dummy pins which are longer than the terminal pins and which are not concerned in conduction with the heat generating element.
The heater is preferably equipped with a sleeve which receives the terminal pins and has heat resistance and insulating properties.
The plate-shaped member preferably comprises a plurality of plate-shaped members, and at least one heat generating element is interposed between at least one pair of plate-shaped members.
A second aspect of the present invention provides a hot plate unit which comprises a casing having an opening portion; a heater arranged on the opening portion and including a first plate-shaped member made from ceramics and a heat generating element arranged on the first plate-shaped member; and a second plate-shaped member interposed between the casing and the heater.
The second plate-shaped member is preferably at least one selected from a group consisting of a metal plate, a ceramic plate, and a resin plate.
The ceramics are preferably nitride ceramics or carbide ceramics.